An airbag module having the features mentioned above is described in document EP 1 790 538 A2. Insofar as the adaptive ventilation opening forming the ventilation area configured on the generic object in order to keep the ventilation opening to be closed, and the release of the ventilation opening to be enabled only at a definable time during the inflation of the airbag, or after the inflation thereof, in the known airbag module, the covering consists of two mutually overlapping fabric cuttings arranged outside on the airbag fabric and covering the ventilation opening. In order to initially keep the fabric cuttings in their position closing the ventilation opening, a restraining strap is provided which is secured with one end to a module-sided holding device arranged in the interior of the airbag. The other end of the restraining strap is led to the outside of the airbag via an opening arranged on the outside of the fabric cutting forming the covering and is secured to the outside of the two mutually overlapping fabric cuttings. The length of the restraining strap is dimensioned such that, when the airbag is inflated, the outer fabric cutting is held by the restraining strap in its extended position and thereby also pressing the inner fabric cutting lying underneath against the airbag fabric, so that the ventilation opening is closed by the two fixed fabric cuttings. Only after activation of the retaining device upon release of the end of the restraining strap secured thereon does the restraining strap sliding through the opening allow an automatic unfolding of the two mutually overlapping fabric cuttings toward the outside as a kind of bird's wings, so that the ventilation opening is thereby released.
The known airbag module is associated with the disadvantage that the opening needed in addition to the ventilation opening and used for the passage of the restraining strap inherently forms an unsealed area in the airbag, which allows an undesirable ventilation of the airbag even when the ventilation opening is to be held closed. Owing to the required threading of the restraining strap through said opening, the installation of the airbag is also hindered. Finally, the opening behavior of the fabric cuttings pressed flat on each other can be insufficient upon release of the restraining strap due to the gas pressure merely acting via the cross section of the ventilation opening.
It is therefore the underlying object of the present invention to design the covering of the ventilation opening and the release thereof in an airbag module having the generic features in a simple and efficient manner.